/*
 * Copyright (C) 2010-2018 Gordon Fraser, Andrea Arcuri and EvoSuite
 * contributors
 *
 * This file is part of EvoSuite.
 *
 * EvoSuite is free software: you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published
 * by the Free Software Foundation, either version 3.0 of the License, or
 * (at your option) any later version.
 *
 * EvoSuite is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with EvoSuite. If not, see <http://www.gnu.org/licenses/>.
 */
package org.evosuite.ga.operators.selection;

import org.evosuite.Properties;
import org.evosuite.ga.Chromosome;
import org.evosuite.utils.Randomness;

import java.util.List;


/**
 * Select an individual from a population as winner of a number of tournaments
 *
 * @author Gordon Fraser
 */
public class TournamentSelection<T extends Chromosome<T>> extends SelectionFunction<T> {

    private static final long serialVersionUID = -7465418404056357932L;

    public TournamentSelection() {
    }

    public TournamentSelection(TournamentSelection<?> other) {
        // empty copy constructor
    }

    /**
     * {@inheritDoc}
     * <p>
     * Perform the tournament on the population, return one index
     */
    @Override
    public int getIndex(List<T> population) {
        int new_num = Randomness.nextInt(population.size());
        int winner = new_num;

        int round = 0;

        while (round < Properties.TOURNAMENT_SIZE - 1) {
            new_num = Randomness.nextInt(population.size());
            T selected = population.get(new_num);

            if (maximize) {
                if (selected.getFitness() > population.get(winner).getFitness()) {
                    winner = new_num;
                }
            } else {
                if (selected.getFitness() < population.get(winner).getFitness()) {
                    winner = new_num;
                }
            }
            round++;
        }

        return winner;
    }

}
